1 List of United States cities by population. ^ 2  Population projection is that of the entity known since 2016 as Ciudad de MÃ©xico and previously as the Distrito Federal. ^  Population estimate is that of the Toronto census division, which consists solely of the City of Toronto.
Lens (optics) For other uses, see Lens. A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (elements), usually arranged along a common axis.
Lens hoods stick out from the lens, so unwanted scratches and dirt on the lens is greatly reduced because the lens becomes harder to reach. To hear the other side of the story, no, you donât need a lens hood. A lens hood is just one more photography item to carry around when you go out shooting.